Southern Pacific's Daylight

Southern Pacific's Daylight ran under Southern Pacific from 1922 to 1971, running a 13-hour schedule between San Fransisco and Los Angeles. 

In its first years of 1922 and 1923, it only ran seasonally between April and November. Daily service began in July of 1923, and in 1924 SP shortened the run to 12 hours. Until the late 1920s the Daylight made no intermediate stops and was the longest nonstop run in the world at the time.

After 1955 the Daylights were running Diesel, long after most other streamlined lines had switched over.

1922-23 advertisement for the Daylight

1961 image of the Coast Daylight after they switched to diesel

Scources:Daylight Wikipedia Page
Note: The Daylight went through a few name changes in its lifetime, I called it just "Daylight" for simplicity's sake, you can see more information in the Wikipedia page.